1. Field of the Invention
This invention relates to heat pumps, and more particularly, to a heat pump system involving simplified controls for maximizing system coefficient of performance, while insuring that safe operating limits are not exceeded.
2. Description Of The Prior Art
Heat pump systems comprise indoor and outdoor coils within a refrigeration loop including a compressor, with the coils trading functions as condensor and evaporator depending upon requirements for heating or cooling of the enclosure housing the indoor coil. Thus, during heating mode, the outdoor coil constitutes an air source evaporator, and the indoor coil acts as a condensor to heat the enclosure, while during the cooling mode, the indoor coil becomes a system evaporator and the outdoor coil becomes the air source condensor. The present invention is concerned with achieving a high coefficient of performance for a heat pump system when the system is operating under heating mode, and the outdoor coil acts as the system evaporator and the indoor coil as the system condensor.
Sometimes there occurs a situation where the heat pump systme operates over extended periods with great differences between the coil surface temperature and with the ambient temperature above that which is necessary for effective heating of the building when the system is under heating mode. This is also important in terms of the number of defrost cycles required to defrost the outdoor coil which functions as the evaporator for the system.
It is therefore an object of the present invention to provide a heat pump control system wherein the saturated suction pressure to the compressor is never allowed to fall further than that which is necessary to adequately heat the building in question and which prevents the saturated condensing pressure from exceeding that which is necessary to adequately heat the building under steadystate conditions.
It is a further objection of this invention to provide an improved air source heat pump system in which the coefficient of performance of the heat pump system is maximized at operating conditions.
It is a further object of the present invention to provide an improved air source heat pump system in which the coil surface temperature is prevented from dropping below the dew point or wet bulb temperature so that, under most conditions, no frosting occurs on the outdoor coil acting as the evaporator for the system, and to virtually eliminate the necessity for defrosting.